Hard copies with higher spatial resolution and better quality full color pictures are always expected in electrophotography technology. The photoreceptor is a key device to acquire the high quality hard copies. While on the one hand it is required to make a precise measurement of charge distribution on a photoreceptor drum, on the other hand the spatial resolution of currently available apparatus is fairly low. Charge distribution measurement with a very high spatial resolution is required both in electrophotography and in semiconductor research. It would be desirable to conduct a study to realize a measurement system which enables the charge distribution measurement to have a spatial resolution less than 10 xcexcm in diameter with utilizing the electrostatic force. Laser printers may already have the spatial resolution of 600 dpi or higher, which indicates that each pixel has approximately 21 xcexcm in diameter. Studies have been made relating to the scanning electrostatic force microscope, however, the theoretical aspects of those studies were only extended to the analysis of a parallel plate model and no further discussion was made relating how the detector needle would affect the charge distribution measurement.
Thus, heretofore one was not able to know how precise in spatial resolution the measurement could be accomplished, how large the charge amount detection had been influenced by the shape of detector and how large the change in film thickness as well as dielectric constant of sample under test would affect the measurement.
In accordance with the present invention, the electrostatic force to be applied to the detector is determined through obtaining the field distribution on several different shaped detectors with the calculation of the voltage distribution near the detector with the Finite Element Method to direct the measurement of the absolute charge amount on surface under test so that one can define the differences between the analysis and the results from the parallel plate model. Of interest is how large the error in the charge detection occurs in conjunction with thickness change of dielectric materials to be tested. There is provided a detector with cantilever which has a proper shape for the spatial resolution of 10xcexc made out of nickel foil for an electrostatic force microscope (EFM) and the electrostatic force which appeared on it has been calculated.